A garage door is a large door on a garage that opens either manually or by an electric motor (a garage door opener) to accommodate automobiles and other vehicles.
In 1926 C. G. Johnson invented the garage door opener. Early electric garage door openers were operated remotely, but not wirelessly. There would be two wired switches, one a keypad outside and the other a switch inside the garage.
As reported in the February 1931 issue of Popular Science, two widely separate teams came up with the idea of a radio-controlled garage door opener.
One used a code pulse system, while the other simply generated white noise on the right frequency to activate. As living spaces became more dense, the white noise system frequently caused the neighbors garage door to open.
The code pulse system soon became the standard. Currently remote garage door openers use a frequency spectrum range between 300-400 MHz and most of the transmitter/receivers rely on hopping or rolling code technology.
A number of people in the United States have suffered death or injury at the mercy of garage door openers with inadequate safety measures.
Many were children. In 1933 the federal government reacted by passing a federal law requiring a minimum level of safety for all garage door openers. The law was effective and since then very few garage door injuries have been repeated.
There are five types of garage door openers. Chain drive, belt drive, screw drive, direct drive, and jackshaft.
Chain drive openers have a chain (similar to a bicycle's) that connects the trolley to the motor.
Belt drive openers use a rubber belt in place of a chain.
Screw drive openers have a long screw inside the track. A trolley connects to this screw.
Direct drive openers have the motor installed inside the trolley and use a gear wheel to guide the trolley along a fixed chain.
Jackshaft openers mount on the wall at either end of the torsion bar. This style of opener consists of a motor that attaches to the side of the torsion rod and moves the door up and down by simply spinning the rod. These openers need a few extra components to function safely for residential use.
Currently, the predominate garage door opening/closing control system in the United States is an electric opener using a Chain drive or a Belt drive to open the garage door. There are a few experimental systems such as a hydraulic cylinder system and even hydraulic system that uses water instead of hydraulic fluid to cause a garage door to open.